Unistrut as Cable Raceway for Open Structure?

miscrms
miscrms Registered Users Posts: 15 ✭✭
in PV Installers Forum - NEC, Wiring, Installation #1
As I understand one of the challenges with mounting solar on a free standing open structure is that the DC cables underneath are "accessible." I'm working on a timber structure over a patio with unistrut racking, and am wondering if there is any reason I can't run the cables into the unistrut and use it as raceway? Unistrut appears to be UL listed, though technically I think it has to be capped to qualify. Also not sure if that only applies to solid strut rather than with holes. In this case I'm hoping capping would be unnecessary as the open side of the strut is facing up at the back of the panels. I'm also wondering what to do with the "extra" cable, could it just be folded over within the strut? Any thoughts on what if any length of exposed cable between the jbox and the strut is likely to be permissible? I'm also planning on using WEEB washers to ground the frames to the strut if that matters.

Any thoughts would be much appreciated!

Rob
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Comments

  • peakbagger
    peakbagger Solar Expert Posts: 341 ✭✭✭
    #2
    Re: Unistrut as Cable Raceway for Open Structure?

    I am really interested in this one as I want to do the same on a polemount. Apparently unistrut can be ordered with no holes so that would cut it down to only needing a cap. I was going to make some sheet metal transitions to the junction box to cover the gap.
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  • jaggedben
    jaggedben Solar Expert Posts: 230 ✭✭
    #3
    Re: Unistrut as Cable Raceway for Open Structure?

    It really comes down to whether your inspector believes you have made the wiring 'not readily accessible.'

    If you need a ladder to get to up to your structure over the patio, then that's usually not going to be considered readily accessible, and you may not have to worry about it. That's the case with rooftop systems. But if the wiring can be reached without the use of any tools, ladders, or lifts, then you might have a problem if your inspector is looking for it. (Many do not.)

    So yes, if you are building your structure with unistrut, then sure, put the wires inside the unistrut. If the inspector doesn't think they are well enough protected, ask him if it would pass his muster to put caps on the strut.

    As for holes vs no holes in the strut, personally I might prefer to see no holes because it is lighter, and will allow water to drain out if the strut is placed across the array. But you could also use solid strut and periodically put weep holes for drainage. If the strut is run up and down then drainage isn't a concern, and you could go solid if you're okay with the weight.
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